Consider first, that the most necessary of all mortifications is that which teaches us to mortify our pride, by the virtue of humility. Humility is the favourite virtue of heaven: all other virtues are nothing without it; they even degenerate into vices when they are tainted with pride. Humility makes us become as little ones; low, mean, and despicable in our own eyes, and willing to be such in the eyes of others. Humility makes us quite sensible of our own demerit, of our misery and sinfulness; teaches us to divest ourselves of all conceit of our own performances or abilities, and to ascribe all good to God alone. Humility sits down in the lowest place; makes us sincerely prefer all others before ourselves, and pretend to no esteem or praise, or honour, or glory, as due to us, or to any excellence of our own; but to be fully and feelingly convinced, not only that we are good for nothing of ourselves, fit for nothing but to do mischief, and deserve nothing but punishment, but also that 'tis owning to God's pure goodness that we are suffered to live upon earth, and that any one at all shows us the least regard, or does us the least service; and that all God's creatures have not a general licence to rise up against us, and to punish us in all manner of ways, for our offences against their creator: in fine, that we were not long since in hell.
Consider 2ndly, that what makes this virtue of humility so acceptable to God is because God is the Truth, and cannot help loving the truth. Now all pride is made up of errors and lies, in taking ourselves to be something, in pretending to what is not our due, or ascribing to ourselves what belongs not to us; or in fine, in being puffed up with the gifts of God, as if they were our own property, or of our own growth. And what is all this but lies? Sacrilegious lies, that offer to rob God of his glory, to challenge to ourselves what belongs to him, and Satan-like to pretend to set ourselves on his throne! But humility goes always hand-in-hand with truth, and ever grounds herself upon the truth, by giving always to God what belongs to God, and to man what belongs to man; by acknowledging, with all simplicity, conviction, and affection, God to be all, and man to be nothing; and by ever ascribing to God whatsoever there is of good in one's self or in anything created; and reserving to one's self nothing but one's own defects. This is true humility, this is the truth that shall stand for ever. This was found, in the greatest perfection, in the most eminent saints upon earth; this shall reign with them in heaven for all eternity, where God shall be all in all for ever.
Consider 3rdly, that humility is not only a virtue absolutely necessary for arriving at Christian perfection, but that there is even no salvation at all for us without it. There is no going to heaven without God's grace; now, 'God resists the proud, and gives his grace to the humble,' St. James iv. 6. And our Lord expressly assures us that 'except we become as little children,' (by humility,) 'we shall not enter into the kingdom of heaven,' Matt. xviii. 3. No, my soul, let us not deceive ourselves, there is no room in heaven for pride. Satan and his companions were cast down from thence by their pride; and their places are not to be filled up but by the humble. Only they that humble themselves upon earth shall be exalted in heaven. The most high and the most holy, who inhabiteth eternity, will only 'dwell with a contrite and humble spirit,' Isaia lvii. 15, and will have respect to none, to bring them to his heavenly kingdom, but such as in their mortal life, by the virtue of humility, are 'poor and little, and of contrite spirit, and tremble at his words,' Isaia lxvi. 2.
Conclude, if thou wouldst have any part with God in his eternal kingdom, to be ever little and humble here upon earth The more thou stoopest down, and castest thyself under the feet of all, by humility, the more God will lift thee up and exalt thee; for he alone is truly great and high, and ever looks down with a favourable eye upon them that are low and humble, to exalt them here by his grace, and hereafter in his glory. But as for such as lift up their heads by pride, and take themselves to be great and high, he keeps them off at a distance and regards them with horror, 'For the proud and arrogant are an abomination to the Lord,' Prov. xvi. 5. Source